Issued July 27,1911. 


U. S. DEPARTMENT OF AGRICULTURE. 

OFFICE OF PUBLIC ROADS—BULLETIN No. 38. 

LOGAN WALLER PAGE, Director. 





BY 

PREVOST HUBBARD, 

CHEMIST, OFFICE OF PUBLIC IlOADS, 

AND 

CHARLES S. REEVE, 

ASSISTANT CHEMIST, OFFICE OF PUBLIC ROADS. 



WASHINGTON : 

GOVERNMENT PRINTING OFFICE. 
1911. 























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Issued July 27, 1911. 


U. S. DEPARTMENT OF AGRICULTURE. 

OFFICE OF PUBLIC ROADS—BULLETIN No. 38. 

LOGAN WALLER PAGE, Director. 


METHODS FOR THE EXAMINATION OF 
BITUMINOUS ROAD MATERIALS. 


BY 


PREVOST HUBBARD, 

*» 

CHEMIST, OFFICE OF PUBLIC ROADS, 

AND 

CHARLES S. REEVE, 

» 

ASSISTANT CHEMIST, OFFICE OF PUBLIC ROADS. 



WASHINGTON : 

GOVERNMENT PRINTING OFFICE. 

1011 . 































OFFICE OF PUBLIC ROADS. 

Logan Waller Page, Director. 

Paul D. Sargent, Assistant Director. 

Vernon M. Peirce, Chief Engineer. 

Prevost Hubbard, Chemist. 

Charles S. Reeve, Assistant Chemist. 

Albert T. Goldbeck, Testing Engineer. 

Edwin C. E. Lord, Petrographer. 

M. 0 . Eldridge, Assistant in Charge of Road Management Investigations. 
Charles H. Hoyt, Assistant in Charge of Bridge Engineering. 

William W. Sniffin, Editorial Cleric and Librarian. 

W. Carl W t yatt, Chief Clerk. 

2 




l\ 


LETTER OF TRANSMITTAL. 


U. S. Department of Agriculture, 

Office of Public Roads, 
Washington, D. C., April 12, 1911. 

Sir: I have the honor to transmit herewith the manuscript of a 
bulletin on Methods for the Examination of Bituminous Road Mate¬ 
rials, by Mr. Prevost Hubbard and Mr. Charles S. Reeve, of this 
office. This bulletin contains complete descriptions of the methods 
of examination for this class of materials as employed at present by 
the office, and should prove of great value to both chemists and 
engineers interested in modern road construction. Moreover, it 
should materially further the general adoption of standard methods, 
a matter which is of the utmost importance at the present time, in 
order that the subject of dust prevention and road preservation may 
be intelligently and systematically studied by road engineers through¬ 
out the country. I recommend that this manuscript be published 
as Bulletin No. 38 of this office. 

Respectfully, Logan Waller Page, 

Director. 

Hon. James Wilson, 

Secretary of Agriculture, 


3 








































































f • 








































CONTENTS. 


Page 

Introduction. 7 

Classification of bituminous road materials. 7 

Scheme of examination. 8 

Specific gravity determination. 9 

Specific viscosity determination. 13 

Float test. 14 

Penetration test. 16 

Melting point determination. 19 

Determination of flash and burning points. 21 

Volatilization test. 23 

Distillation test. 24 

Determination of bitumen soluble in carbon disulphide. 27 

Determination of bitumen insoluble in paraffin naphtha. 30 

Determination of bitumen insoluble in carbon tetrachloride. 31 

Determination of fixed carbon. 32 

Determination of paraffin scale. 33 

Extraction of bituminous aggregates. 35 

Grading the mineral aggregate. 38 

Determination of voids in the mineral aggregate. 39 

Appendix. 40 

Laboratory equipment. 40 

.Metric conversion tables. 42 

Comparison of degrees Baume and specific gravity. 42 

Comparison of centigrade and Fahrenheit degrees. 43 

Forms for reporting tests. 43 


ILLUSTRATIONS. 


Fig. I. Hydrometer method of determining specific gravity.. 

2. Office of Public Roads pycnometer. 

3. Displacement method of determining specific gravity 

4. Engler viscosimeter. 

5. New York Testing Laboratory float apparatus. 

6. Dow penetration machine. 

7. New York Testing Laboratory penetrometer. 

8. Office of Public Roads bitumen holder. 

9. Melting point apparatus. 

10. New York State Board of Health oil tester. 

11. New York Testing Laboratory oven. 

12. Asbestos hood for retort. 

13. Distillation apparatus. 

14. Apparatus for determining soluble bitumen. 

15. Apparatus for determining fixed carbon. 

16. Apparatus for determining paraffin scale. 

17. Office of Public Roads centrifuge extractor. 

18. Recovery apparatus. 


Page. 

8 

11 

12 

13 

15 

17 

17 

19 

20 
22 
23 

25 

26 
27 
32 
34 

36 

37 


5 






















































































- 































































































METHODS FOR THE EXAMINATION OF BITUMINOUS ROAD 

MATERIALS. 


INTRODUCTION. 

The object of this bulletin is to present a description of the methods, 
now in use by the Office of Public Roads, for the examination of 
bituminous road materials, in such form that any intelligent person 
may, with a little practice and the proper equipment, make such 
examinations. With this object in view the various tests have been 
described rather more in detail than would be necessary if they were 
intended for the use of chemists only, and illustrations of practically 
all of the apparatus required have also been included. 

It is to be regretted that no standard methods of examining 
bituminous road materials have been generally adopted, as the 
necessity for such standards has become imperative. The Office of 
Public Roads has given considerable attention to this matter, both 
with respect to investigations conducted in its laboratories and 
through cooperation with certain technical societies interested in the 
testing of materials. While it is realized that the following scheme 
of examination is by no means perfect, and may in the future be 
improved, it has nevertheless been of great service in classifying 
bituminous road materials and determining their suitability for use 
according to various methods of application and construction. 
Letters requesting such information have been received constantly 
by the office during the past few years, and this bulletin has there¬ 
fore been written to meet such demands. 

CLASSIFICATION OF BITUMINOUS ROAD MATERIALS. 

For the purpose of examination bituminous road materials may be 
classified under the following headings: 

1. Petroleums and petroleum products, including residual petroleums, fluxes, oil- 
asphalts, and fluxed or cut-back oil-asphalts. 

2. Malthas. 

3. Asphalts and other solid native bitumens, and asphaltic cements produced by 
fluxing them. 

4. Tars and tar products. 


7 



8 


EXAMINATION OF BITUMINOUS ROAD MATERIALS. 


5. Mixtures of tar with petroleum or asphalt products, bituminous emulsions, and 
factitious asphalts. 

6. Bituminous aggregates, including rock asphalts or bituminous rocks, bituminous 
concrete and asphalt or other bituminous topping. 

SCHEME OF EXAMINATION. 


All petroleum, maltha, and solid native bitumen products are sub¬ 
jected to the following tests: 

Specific gravity. 

Volatilization at 163° C. 

Bitumen soluble in carbon disulphide. 

Bitumen insoluble in 86° B. paraffin naphwii 
Fixed carbon. 


Of these types the very fluid and sometimes the more viscous 
products may be subjected to the viscosity, flash, and burning-point 
determinations. Very viscous materials, too soft for the 
penetration test, are subjected to the float test, and semi¬ 
solid and solid products to the penetration test. If the 
material is hard at ordinary temperatures, a melting-point 
determination may also prove of value. Sometimes two 
or more of the above-mentioned tests, depending upon 
the character of the material and the use to which it is to 
be put, may be made to advantage on a single material. 
When for any reason it is suspected that the material 
under examination has been overheated and possibly 

cracked during proc- 


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ess of manufacture, or 

prepared from a solid 

native indurated bitu- 

> 

men, the d etermination 
of bitumen insoluble in 
carbon tetrachloride 
may be made. The 
paraffin scale determi¬ 
nation is made on those 
materials which are to 
be identified as being 

v o 

partly composed of heavy paraffin hydrocarbons. The residue obtained 
from the volatilization test is usually subjected to either the float or 
penetration test, and in addition it may be subjected to aii} r or all of 
the above-described tests as occasion may require. 

Tar and tar products are subjected to the following tests: 


a 

Fig. 1.—Hydrometer method of determining specific gravity. 


Specific gravity. 

Distillation. 

Bitumen soluble in carbon disulphide. 












SPECIFIC GRAVITY DETERMINATION. 


9 


In addition, the viscosity test may be employed for fluid products 
and it is highly desirable that the float test be made on all of the 
viscous and semisolid tar products. The more or less solid refined 
tars or tar pitches are also subjected to the melting-point determina¬ 
tion*. 

Emulsions, mixtures of tar with petroleum or asphalt products, 
and factitious asphalts can not be satisfactorily examined accord¬ 
ing to any one predetermined scheme, and at the present time this 
matter must be left to the judgment and experience of the analyst. 
Practically all of the methods described in this bulletin are, however, 
applicable to such materials, and for a given material those methods 
should be selected which will give the most information concern¬ 
ing its character and suitability for the specific use for which it is 
intended. 

Bituminous aggregates are first of all examined for the percentage 
of bitumen soluble in carbon disulphide. If the amount is in excess 
of 5 per cent, an extraction is then made on a large sample and the 
recovered bitumen is examined according to one of the above-men¬ 
tioned schemes if it can be identified, or, if not, it is subjected to those 
tests which are of most value as suggested under mixed tar and oil 
or asphalt products, and factitious asphalts. The extracted mineral 
aggregate is usually quantitatively graded and, if it is to be used or 
has been used as an integral part of the road proper, its percentage of 
voids is also determined. 

Forms for reporting the results of examination of bituminous road 
materials according to the methods described in this bulletin are 
given in the appendix. 

SPECIFIC GRAVITY DETERMINATION. 

HYDROMETER METHOD (USED FOR THIN FLUID BITUMENS). 

EQUIPMENT. 

1 hydrometer jar approximately 35 centimeters long and 5 centimeters in diameter. 

(Fig. 1-a.) 

1 1-pint tin cup, seamless type. (Fig. 1-6.) 

1 enamel-ware dish approximately 2 inches deep and 9 inches in diameter. (Fig. 1-c.) 
1 chemical thermometer reading from —10° C. to 110° C. (Fig. l-d.) 

1 set of hydrometers—those with a double scale at 15.5° C. (60° F.), one for Baum5 
and one for a direct specific gravity reading to the third decimal place are used 
by the Office of Public Roads. (Fig. 1-e.) 

1 hydrometer reading from 0.800 to 0.900 specific gravity. 

1 hydrometer reading from 0.900 to 1.000 specific gravity. 

1 hydrometer reading from 1.000 to 1.200 specific gravity. 

1 hydrometer reading from 1.200 to 1.400 specific gravity. 

91501°—Bull. 38—11-2 



10 


EXAMINATION OF BITUMINOUS ROAD MATERIALS. 


METHOD. 

The specific gravity of thin fluid bituminous road materials is 
determined at 25° C. as compared with water at that temperature. 
This may be done with the above-mentioned apparatus by first p.our- 
ing a sufficient quantity of the material into the tin cup, which is then 
placed in the large dish containing cold or warm water as occasion 
may require. The material in the cup should be stirred with the 
thermometer until it is brought to a temperature of 25° C., after 
which it should be immediately poured into the hydrometer jar and 
its gravity determined by means of the proper hydrometer. In case 
the hydrometer sinks slowly, owing to the viscosity of the material, 
it should be given sufficient time to come to a definite resting point, 
and this point should be checked by raising the hydrometer and allow¬ 
ing it to sink a second time. The hydrometer should never be pushed 
below the point at which it naturally comes to rest until the last read¬ 
ing has been made. It may then be pushed below the reading for a 
distance of three or four of the small divisions on the scale, whereupon 
it should immediately begin to rise. If it fails to do so, the material 
is too viscous for the hydrometer method, and the pycnometer method 
should be employed. 

The direct specific gravity reading obtained by the foregoing 
method is based upon water at 15.5° C. taken as unity. For all prac¬ 
tical purposes this reading may be corrected to water at 25° C., consid¬ 
ered as unity, by multiplying it by 1.002. Thus: 

Specific gravity 25° C./25° C. = specific gravity 25° C./15.5 0 C. X 1.002. 

PYCNOMETER METHOD (USED FOR VISCOUS FLUID AND SEMISOLID 

BITUMENS AND EMULSIONS). 

EQUIPMENT. 

1 large metal kitchen spoon. 

1 Bunsen burner and rubber tubing. 

1 250 cubic centimeter low-form glass beaker. 

1 chemical thermometer reading from —10° C. to 110°C. 

1 special pycnometer. (Fig. 2.) 

1 analytical balance, capacity 100 grams, sensitive to 0.1 milligram. 

METHOD. 

The inconvenience and difficulty of employing the ordinary 
narrow-neck pycnometer when determining the specific gravity of 
viscous fluid and semisolid bitumens has led to the use of the special 
form shown in figure 2. 

This pycnometer consists of a fairly heavy, straight-walled glass 
tube, 70 millimeters long and 22 millimeters in diameter, ground to 
receive a solid glass stopper with a hole of 1.6 millimeters bore in 


SPECIFIC GRAVITY DETERMINATION. 


11 


xn 


ii 

■---it - - , 


place of the usual capillary opening. The lower part of this stopper 
is made concave in order to allow all air bubbles to escape through 
the bore. The depth of the cup-shaped depression is 4.8 millimeters 
at the center. The stoppered tube has a capacity of about 24 cubic 
centimeters and when empty weighs about 28 grams. Its principal 
advantages are (1) that any desired amount of bitumen may be 
poured in without touching the sides above the level desired; (2) 
it is easily cleaned; (3) on account of the 1.6-millimeter bore the 
stopper can be more easily inserted when the tube is filled with a very 
viscous oil than if it contained a capillary opening. 

When working with semisolid bitumens which are too soft to be 
broken and handled in fragments, the following method 
of determining their specific gravity has been em¬ 
ployed with good results. The clean, dry pycnometer 
is first weighed empty and this weight is called “a.” 

It is then filled in the usual manner with freshly dis¬ 
tilled water at 25° C., and the weight is again taken 
and called “b.” A small amount of the bitumen 
should be placed in the spoon and brought to a fluid 
condition by the gentle application of heat, with 
care that no loss by evaporation occurs. When 
sufficiently fluid, enough is poured into the dry 
pycnometer, which may also be warmed, to fill it 
about half full, without allowing the material to touch 
the sides of the tube above the desired level. The 
tube and contents are then allowed to cool to room 
temperature, after which the tube is carefully weighed 
with the stopper. This weight is called “c.” Distilled 
water, at 25°C.,is then poured in until the pycnom¬ 
eter is full. After this the stopper is inserted, and 
the whole cooled to 25° C. by a 30-minute immersion 
in a beaker of distilled water maintained at this tem¬ 
perature. All surplus moisture is then removed with 
a soft cloth, and the pycnometer and contents are 
weighed. This weight is called “d.” From the weights obtained 
the specific gravity of the bitumen may be readily calculated by the 
following formula: 

Specific gravity 25° C./25 0 C. = 



Fig. 2—Office of 
Public Roads 
pycnometer 
(Hubbard type). 


Both “a” and “b” are constants and need be determined but once. 
It is, therefore, necessary to make only two weighings for all deter¬ 
minations after the first. Results obtained according to the method 
given above are accurate to within 2 units in the third decimal place, 
while the open-tube method commonly employed is accurate to the 
second decimal place only. 








12 


EXAMINATION OF BITUMINOUS ROAD MATERIALS. 


The specific gravity of fluid bitumens may be determined in the 
ordinary manner with this pycnometer by completely filling it with 
the material and dividing the weight of the bitumen thus obtained by 
that of the same volume of water. 

The pycnometer may be readily cleaned by placing it in a hot-air 
bath until the bitumen is sufficiently fluid to pour. As much is 
drained out as possible and the interior swabbed with a piece of 
cotton waste. It is then rinsed clean with a little carbon disulphide, 
and after drying is again ready for use. 


DISPLACEMENT METHOD (USED FOR HARD SOLID BITUMENS). 

EQUIPMENT. 

1 chemical thermometer reading from —10° C. to 110° C. 

1 analytical balance, capacity 100 grams, sensitive to 0.1 milligram. 

1 wood or metal platform. 

1 150 cubic centimeter low-form glass beaker. 

1 piece of fine silk thread. 

METHOD. 


For materials which rue hard enough to be broken and handled 
in fragments at room temperature, the following method will prove 

convenient. A small 
fragment of the bitu¬ 
men (about 1 cc.) is 
suspended by means 
of a silk thread from 
the hook on one of the 
pan supports, about 
1| inches above the 
pan, and weighed. 
This weight is called 
“ a. ” It is then 
weighed immersed in 
water at 25° C., as 

shown in figure 3, and 
Fig. 3.—Displacement method of determining specific gravity. ^ , , . ni . 

tins weight is called 

“b.” The specific gravity may then be calculated by means of the 
following formula: 



Specific gravity =- 


a 

a-b. 


USE OF SPECIFIC GRAVITY DETERMINATION. 

The specific gravity determination is made on all bitumens con¬ 
taining less than 50 per cent mineral matter, and also on bitumens 
recovered from bituminous aggregates. The specific gravity is 
usually reported to the third decimal place. 































SPECIFIC VISCOSITY DETERMINATION. 


13 


SPECIFIC VISCOSITY DETERMINATION. 

EQUIPMENT. 

1 Engler viscosimeter complete with thermometers, burner, and rubber tubing. 

1100 cubic centimeter cylindrical glass graduate. 

1 stop watch. 

METHOD. 

The viscosity of fluid bituminous road binders may be determined 
at any desired temperature by means of the Engler viscosimeter. 
This apparatus is shown in figure 4, and may be described as follows: 
a is a brass vessel for bolding the material to be tested, and may be 
closed by the cover b. 
outflow tube c, exactly 
20 millimeters long, 
with a diameter on 
top of 2.9 millimeters 
and on the bottom of 
2.8 millimeters. This 
tube can be closed and 
opened by the pointed 
hardwood stopper d. 

Pointed metal projec¬ 
tions are placed on the 
inside of a at equal dis¬ 
tances from the bottom 
and serve for measur¬ 
ing the charge of mate¬ 
rial which is 240 cubic 
centimeters. The ther¬ 
mometer e is used to 
ascertain the tempera¬ 
ture of the material to 
be tested. The vessel 
a is surrounded by a brass jacket/, which holds the material used 
as a heating bath, either water or cottonseed oil, according to the 
temperature at which the test is to be made. A tripod g serves as a 
support for the apparatus and also carries a ring burner h by means of 
which the bath is directly heated. The measuring cylinder of 100 
cubic centimeters capacity, which is sufficiently accurate for work 
with road materials, is placed directly under the outflow tube. 

As all viscosity determinations should be compared with that of 
water at 25° C., the apparatus should be previously calibrated as follows: 
The cup and outlet tube should first be scrupulously cleaned. A piece 
of soft tissue paper is convenient for cleaning the latter. The stopper 
is then inserted in the tube and the cup filled with water at 25° C. 
to the top of the projections. The measuring cylinder should be 


To the conical bottom of a is fitted a conical 





































14 


EXAMINATION OF BITUMINOUS ROAD MATERIALS. 


placed directly under the outflow tube so that the material, upon 
flowing out, will not touch the sides, and the stopper may then be 
removed. The time required both for 50 and 100 cubic centimeters 
to run out should be ascertained by means of a stop watch and the 
results so obtained should be checked a number of times. The time 
required for 50 cubic centimeters of water should be about 11 seconds 
and for 100 cubic centimeters about 22.8 seconds. 

Bituminous road materials are tested in the same manner as water 
and the temperature at which the test is made is controlled by the 
bath. The material should be brought to the desired temperature 
and maintained there for at least three minutes before making the 
test. The results are expressed as specific viscosity compared with 
water at 25° C., as follows: 

Specific viscos- __ seconds for passage of given volum e at a° C. 
ity at a° C. seconds for passage of same volume of water at 25° C. 

USE OF VISCOSITY DETERMINATION. 

For all thin fluid bituminous road materials the specific viscosity 
is determined at 25° C. with 100 cubic centimeters. Viscous fluid 
products are run at 50° C. with 50 cubic centimeters and very viscous 
products at 100° C. or over with 50 cubic centimeters. This test 
is not always made on the materials above mentioned, but is a useful 
one when they are required to have a given degree of fluidity at a given 
temperature. 

FLOAT TEST. 

EQUIPMENT. 

1 aluminum float or saucer. (Fig. 5-a.) 

2 conical brass collars. (Fig. 5-6.) 

2 1-quart tin cups, seamless. 

2 chemical thermometers reading from —10° C. to 110° C. 

1 iron tripod. 

1 Bunsen burner and rubber tubing. 

1 burette clamp and support. 

1 large metal kitchen spoon. 

1 brass plate 5 by 8 centimeters. 

1 steel spatula. 

1 stop watch. 

METHOD. 

The float apparatus consists of two parts, an aluminum float or 
saucer (fig. 5-a) and a conical brass collar (fig. 5-&). The two parts 
are made separately, so that one float may be used with a number of 
brass collars. 

In making the test the brass collar is placed with the small end 
down on the brass plate, which has been previously amalgamated 
with mercury by first rubbing it with a dilute solution of mercuric 



FLOAT TEST. 


15 


chloride or nitrate and then with mercury. A small quantity of 
the material to be tested is heated in the metal spoon until quite 
fluid, with care that it suffers no appreciable loss by volatiliza¬ 
tion and that it is kept free from air bubbles. It is then poured 
into the collar in a thin stream until slightly more than level 
with the top. The surplus may be removed, after the material has 
cooled to room temperature, by means of a spatula blade which has 
been slightly heated. The collar and plate are then placed in one 
of the tin cups containing ice water maintained at 5° C., and left 
in this bath for at least 15 minutes. Meanwhile the other cup is filled 
about three-fourths full of water and placed on the tripod, and the 
water is heated to any desired temperature at which the test is to 
be made. This temperature should be accurately maintained, and 



• Fig. 5.—New York testing laboratory float apparatus. 

should at no time throughout the entire test be allowed to vary 
more than one-half a degree centigrade from the temperature selected. 
After the material to be tested has been kept in the ice water for at 
least 15 minutes, the collar and contents are removed from the plate 
and screwed into the aluminum float, which is then immediately 
floated in the warmed bath. As the plug of bituminous material 
becomes warm and fluid, it is gradually forced upward and out of the 
collar, until water gains entrance to the saucer and causes it to sink. 

The time in seconds between placing the apparatus on the water 
and when the water breaks through the bitumen is determined by 
means of a stop watch and is taken as a measure of the consistency 
of the material under examination. 






















16 


EXAMINATION OF BITUMINOUS ROAD MATERIALS. 


USE OF THE FLOAT TEST. 

This test is always made on viscous and semisolid refined tars, 
and often on the viscous and semisolid petroleum and asphalt prod¬ 
ucts, although, when the penetration test can be employed on the 
two latter classes of material, the float test is not always considered 
necessary. For the more fluid products the test is made at 32° C. 
and for the semisolid materials, at 50° C. When the material under 
examination is quite hard, the test may be run at 100° C. 

The float test is a most convenient one for roughly checking the 
quality of different shipments of bituminous material furnished under 
specifications. 

PENETRATION TEST. 

EQUIPMENT. 

1 penetrometer complete, with a seconds pendulum or chronometer. (Figs. G and 7.) 
1 tin box approximately 5 centimeters in diameter by 3.5 centimeters in height. 

1 brass bitumen holder. (Fig. 8.) 

1 glass penetration dish approximately 10 centimeters in diameter by 6 centimeters 
high. 

1 enamel-ware dish approximately 3 inches deep and 9 inches in diameter. 

1 chemical thermometer reading from —10° C. to 110° C. 

METHOD. 

The object of the penetration test is to ascertain the consistency 
of the material under examination by determining the distance a 
weighted needle will penetrate into it at a given temperature. A 
standard No. 2 cambric needle is employed for this purpose and this 
needle is usually weighted with 100 grams. The depth of penetra¬ 
tion is determined upon the bitumen maintained at 25° 0., while 
the load is applied for five seconds. 

The penetration apparatus shown in figure 6 consists of a No. 2 
needle a, inserted in a short brass rod, which is held in the aluminum 
rod & by a binding screw. The aluminum rod is secured in a frame¬ 
work so weighted and balanced that, when it is supported on the point 
of the needle, the framework and rod will stand in an upright posi¬ 
tion, allowing the needle to penetrate perpendicularly without the 
aid of a support. 

The frame, aluminum rod, and needle w r eigh 100 grams with the 
weight c on the bottom of the frame, while without the weight they 
weigh 50 grams. Figure 6 shows the needle and weighted frame, 
together with side and front views of the entire apparatus, put 
together and ready for making a penetration. The shelf for the 
sample is marked d; e is the clamp to hold the aluminum rod until 
it is desired to make a test; and / is a button which, when pressed, 
opens the clamp. By turning this button while the clamp is being 
held open, it will lock and keep the clamp from closing until unlocked. 


PENETRATION TEST. 


17 


The device for measuring the distance penetrated by the needle 
consists of a rack, with a foot g. The movement of this rack turns 
a pinion, to which is attached the hand which indicates on the dial 
h the vertical distance 
covered by the rack. 

One division of the dial 
corresponds to a move¬ 
ment of 0.1 millimeter 
by the rack. The rack 
may be raised or low¬ 
ered by moving the 
counterweight i up or 
down. The tin box 
containing the sample 
to be tested is marked 



water contained in 

the glass cup in order 
to maintain a constant 
temperature. 

This apparatus is 

known as the Dow Fig. 6.—Dow penetration machine. 

penetration machine. Another type of machine known as the New 
York Testing Laboratory penetrometer, based upon the same general 

principle, and using 
the same standards, is 
at present employed 
by the Office of Public 
Roads. This pene¬ 
trometer is shown in 
figure 7. Both ma¬ 
chines give practically 
the same results, if 
operated under the 
same conditions, and 
it is therefore con¬ 
sidered unnecessary to 
include a description 
of the latter. 

A cup suitable for 
holding the box con¬ 
taining the test sam¬ 
ple during penetration is conveniently made from a glass crystal¬ 
lizing dish 10 centimeters in diameter, with straight sides about 6 
centimeters high. Three right triangles with right angle sides 1 
and 5 centimeters, respectively, are cut from y^-inch sheet metal. 

91501°—Bull. 38—11-3 




zse 


Fig. 7.—New York Testing Laboratory penetrometer. 





















































































































18 


EXAMINATION OF BITUMINOUS ROAD MATERIALS. 


Some solid bitumen is melted in the bottom of the dish form¬ 
ing a layer about J-inch thick, into which the triangles are placed, 
resting on the side five centimeters long. Their apexes should meet 
at the center, with their short sides dividing the circumference of the 
dish into three equal arcs. When the bitumen has hardened, the 
triangles give a firm support for circular boxes, and the possibility 
of any rocking motion and consequent faulty results is avoided. 

The penetration test is made as follows: A sample of the material 
to be tested is first warmed sufficiently to flow, and poured into the 
tin box. The box and contents, after cooling, are then immersed in 
water maintained at the temperature at which the test is to be made, 
and allowed to remain immersed for at least 30 minutes. The 
sample in the tin box should now be placed in the glass cup and 
removed in it, covered with as much water as convenient without 
spilling, to the shelf d. The brass rod with the needle is inserted into 
b and secured by tightening the binding screw. The rod is lowered 
until the point of the needle almost touches the surface of the sample; 
then, by grasping the frame with both hands it is cautiously pulled 
down until the needle just comes in contact with the surface of the 
sample. This can be seen best by having a light so situated that, 
upon looking through the sides of the glass cup, the needle will be 
reflected from the surface of the sample. After thus setting the needle, 
the counterweight is slowly raised until the foot of the rack rests on the 
head of the rod and a reading of the dial taken. The clamp is then 
opened wide by pressing the button and held in this position for 
exactly five seconds, as determined by the pendulum or chronometer. 
The rack is then lowered until it rests on the rod, and the difference 
between the first and second readings of the dial in millimeters is 
taken as the distance penetrated by the needle. 

Owing to the susceptibility of certain bitumens to slight changes 
in temperature, the water bath should be accurately maintained at 
the desired temperature, both before and during the test, and, when 
the room temperature differs greatly from that of the bath, the water 
in the glass cup should be renewed after each test. An average of 
from three to five tests, which should not differ more than 0.3 milli¬ 
meter between maximum and minimum, is taken as the penetration 
of the sample. 

The needle should be removed and thoroughly cleaned by wiping 
with a dry cloth, after which it is ready for another test. The point 
of the needle should be examined from time to time with a magnifying 
glass to see that it is not injured in any way. If it is found defective, 
it may be removed by heating the brass rod and withdrawing with 
pliers. A new needle may then be inserted in the heated brass rod, 
and held firmly in place by a drop of soft solder. 


MELTING POINT DETERMINATION. 


19 


USE OF PENETRATION TEST. 



This test is made on all semisolid and solid oil-asphalts, asphaltic 
cements, and native asphalts, but seldom on tar products. It is 
also often made on the residues of materials subjected to the volatiliza¬ 
tion tests, when they are sufficiently hard. For work on residues, 
which seldom amount to more than 20 cubic centimeters, the type of 
container shown in figure 8 will be found convenient in order to 
obtain the necessary depth of material. This container is made to 
hold five samples. It consists of a brass cylinder 50 millimeters in 
diameter and 30 millimeters high, resting upon a brass plate. The 
interior of this cylinder is partitioned off into five compartments of 
about 12 cubic centimeters capacity 
each, one consisting of a small 
brass cylinder 23 millimeters in 
diameter, concentric with the large 
cylinder. Four flat partitions, two 
of which are at right angles to 
the other two, connect the small 
cylinder with the larger, thus form¬ 
ing four additional compartments. 

The inner cylinder and partitions 
are fastened together, and can be 
removed from the outer cylinder. 

While the standard conditions 
under which this test is made call 
for a 100-gram load applied for five 
seconds on the material maintained 
at a temperature of 25° C., it is 
sometimes desirable, when very soft 
materials are tested, to make the 
test with a 50-gram weight. In 
order to ascertain how susceptible 
a material may be to temperature changes, tests may be made 
at any other desired temperatures, preferably 0° C., with a 200- 
gram weight for one minute, and at 38° or 46° C. with a 50-gram 
weight for five seconds. 

In all cases the results of tests should be reported in millimeters and 
tenths of millimeters, as follows, showing all the conditions in order 
that no misinterpretation of results may occur: 

Penetration (No. 2 N, -seconds,-grams at-° C.)= mm. 

MELTING POINT DETERMINATION. 

EQUIPMENT. 

1 iron tripod. 

1 Bunsen burner and rubber tubing. 

1 piece of wire gauze 10 centimeters square. 


Fig. 8.—Office of Public Roads bitumen 
bolder (Draper type). 


































20 


EXAMINATION OF BITUMINOUS ROAD MATERIALS. 


1 800 cubic centimeter Jena glass beaker, low form. (Fig. 9-a.) 

1 400 cubic centimeter Jena glass beaker, tall, without lip. (Fig. 9-6.) 

1 iron ring support (ring 7.5 centimeters in diameter) and burette clamp. (Fig.9-c.) 
1 metal cover. (Fig. 9-d.) 

1 object glass. 

1 piece of wire (No. 12 Brown & Sharpe gauge) 20 centimeters in length, bent. (Fig. 
9-e.) 

1 chemical thermometer reading from 0° C. to 250° C. 

1 cubical brass mold. (Fig. 9-/.) 

1 large metal kitchen spoon. 

1 steel spatula. 

METHOD. 

Since bitumens are mixtures of various organic compounds, they 
can have no true melting point, but an arbitrary method for deter¬ 
mining the so-called melting point of those materials sufficiently solid to 
maintain their form for some time under normal conditions is of value 

as a means of identifi¬ 
cation and for control 
work. A number of 
methods have been 
tried, but the follow¬ 
ing has been selected 
as the most conven¬ 
ient and accurate for 
such materials. 

The material under 
examination is first 
melted in the spoon 
by the gentle appli¬ 
cation of heat until 
sufficiently fluid to 
pour readily. Care 
must be taken that 
it suffers no appreciable loss by volatilization. It is then poured 
into the I-incli brass cubical mold, which has been amalgamated 
with mercury and which is placed on an amalgamated brass plate. 
The brass may be amalgamated by washing it first with a dilute solu¬ 
tion of mercuric chloride or nitrate, after which the mercury is 
rubbed into the surface. By this means the bitumen is, to a con¬ 
siderable extent, prevented from sticking to the sides of the mold 
The hot material should slightly more than fill the mold and, when 
cooled, the excess may be cut off with a hot spatula. 

After cooling to room temperature, the cube is removed from the 
mold and fastened upon the lower arm of a No. 12 wire (Brown & 
Sharpe gauge), bent at right angles and suspended beside a thermome¬ 
ter in a covered Jena glass beaker of 400 cubic centimeters capacity 
which is placed in a water bath, or, for high temperatures, a cottonseed- 
oil bath. The wire should be passed through the center of two opnosite 



Fig. 9.—Melting point apparatus. 










































DETERMINATION OF FLASH AND BURNING POINTS. 


21 


faces of the cube, which is suspended with its base 1 inch above the 
bottom of the beaker. The water or oil bath consists of an 800-cubic 
centimeter low-form Jena glass beaker suitably mounted for the 
application of heat from below. The beaker in which the cube is 
suspended is of the tail-form Jena type without lip. The metal cover 
has two openings as shown in figure 5 -d. A cork, through which 
passes the upper arm of the wire, is inserted in one hole and the 
thermometer in the other. The bulb of the thermometer should be 
just level with the cube and at an equal distance from the side of the 
beaker. In order that a reading of the thermometer may be made, if 
necessary, at the point which passes through the cover, the hole is 
made triangular in shape and covered with an ordinary object glass 
through which the stem of the thermometer may be seen. Readings 
made through this glass should be calibrated to the angle of observa¬ 
tion, which may be made constant by always sighting from the front 
edge of the opening to any given point on the stem of the thermometer 
below the cover. 

After the test specimen has been placed in the apparatus, the liquid 
in the outer vessel is heated in such a manner that the thermometer 
registers an increase of 5° C. per minute. The temperature at which 
the bitumen touches a piece of paper placed in the bottom of the 
beaker is taken as the melting point. Determinations made in the 
manner described should not vary more than 2° for different tests of 
the same material. At the beginning of this test the temperature of 
both bitumen and bath should be approximately 25° C. 

USE OF MELTING-POINT DETERMINATION. 

The melting-point determination should be made on all bituminous 
road binders sufficiently hard to be handled at room temperature after 
removing from the mold. This test is not usually required for 
bitumens which are to be cut with a nonvolatile flux before use. 

DETERMINATION OF FLASH AND BURNING POINTS. 

EQUIPMENT. 

1 New York State Board of Health oil tester with Bunsen burner. (Fig. 10.) 

1 chemical thermometer reading from 0° C. to 400° C. 

1 piece of 6-millimeter glass tubing, 6 centimeters in length, one end of which has 
been drawn to a 1-millimeter opening. Soft rubber tubing for gas connection. 

METHOD. 

While for all ordinary purposes the open-cup method of determining 
the flash and burning points of bituminous road materials is suffi¬ 
ciently accurate, the closed-cup method described below is to be 
preferred. 


22 


EXAMINATION OF BITUMINOUS ROAD MATERIALS. 


The oil tester shown in figure 10 consists of a copper oil cup a of 
about 300 cubic centimeters capacity, which is heated in a water or 
oil bath 1) by a small Bunsen flame. The cup is provided with a 
glass cover c, carrying a thermometer d, and a hole e for inserting 
the testing flame. The testing flame is obtained from a jet of gas 
passed through the piece of glass tubing and should be about 5 milli¬ 
meters in length. 

The flash test is made as follows: The oil cup should first be 
removed and the bath filled with water or cottonseed oil. The oil may 

always be used and is necessaiy for 
bitumens flashing at a temperature 
of over 100° C. The oil cup should 
be replaced and filled with the 
material to be tested to within 3 
millimeters of the flange joining the 
cup and the vapor chamber above. 
The glass cover is then placed on 
the oil cup and the thermometer so 
adjusted that its bulb is just covered 
by the bituminous material. The 
Bunsen flame should be applied in 
such a manner that the temperature 
of the material in the cup is raised 
at the rate of about 5° C. per min¬ 
ute. From time to time the testing 
flame is inserted in the opening in 
the cover to about half way between 
the surface of the material and the 
cover. The appearance of. a faint 
bluish flame over the entire surface 
of the bitumen shows that the flash 
point has been reached and the tem¬ 
perature at this point is taken. 

The burning point of the material 
may now be obtained by removing 
the glass cover and replacing the 
thermometer in a wire frame. The 
temperature is raised at the same rate and the material tested as 
before. The temperature at which the material ignites and burns is 
taken as the burning point. 

At the conclusion of this test the flame should not be blown out for 
danger of splashing the hot material. A metal cover or extinguisher 
should be employed for tins purpose by placing it over the ignited 
material. 




Fig. 10. —New York State Board of Health 
oil tester. 

































































VOLATILIZATION TEST. 


23 


USE OF FLASH POINT AND BURNING POINT DETERMINATIONS. 

The flash and burning point determinations should be made of all 
fluid bituminous road materials which have to be heated before 
application and upon all semisolid products which show a loss by the 
volatilization test at 163° C. of over 5 per cent. It should also be 
made upon fluxes which are to be used in cutting hard bitumens. 

VOLATILIZATION TEST. 

EQUIPMENT. 

1 constant-temperature hot-air oven with rubber tubing. (Fig. ]I.) 

1 thermo-regulator. (Fig. 11-a.) 

2 chemical thermometers reading from —10° C. to 250° C. 

1 tin box, 6 centimeters in diameter by 2 centimeters deep. 

1 analytical balance, capacity 100 grams, sensitive to 0.1 milligram. 

METHOD. 

The object of the volatilization test is to determine the percentage 
of loss which the material undergoes when 20 grams in a standard¬ 
sized container are 
subjected to a uni¬ 
form temperature of 
163° C. for five hours, 
and also to ascertain 
any changes in the 
character of the ma¬ 
terial due to such 
heating. 

The oven shown in 
figure 11, known as 
the New York Test¬ 
ing Laboratory oven, 
is used by the Office 
of Public Loads, al¬ 
though any other form may be used that will give a uniform tempera¬ 
ture throughout all parts where samples are placed. The bulb of 
one of the thermometers is immersed in a sample of some fluid, 
nonvolatile bitumen, while the other is kept in air at the same level. 
The first thermometer serves to show the temperature of the samples 
during the test, while the latter gives prompt warning of any sudden 
changes in temperature due to irregularities in the gas pressure, etc. 

Before making the test the interior of the oven should show a tem¬ 
perature of 163° C. as registered by the thermometer in air. The tin 
box is accurately weighed after carefully wiping with a towel to remove 
any grease or dirt. About 20 grams of the material to be tested is 
then placed in the box. The material may then be weighed on a 
rough balance, if one is at hand, after which the accurate weight, 































24 


EXAMINATION OF BITUMINOUS ROAD MATERIALS. 


which should not vary more than 0.2 gram from the specified amount, 
is obtained. It may be necessary to warm some of the material 
in order to handle it conveniently, after which it must be allowed 
to cool before determining the accurate weight. 

The sample should now be placed in the oven, where it is allowed to 
remain for a period of five hours, during which time the temperature 
as shown by the thermometer in bitumen should not vary at any time 
more than 2° C. from 163° C. The sample is then removed from the 
oven, allowed to cool, and re weighed. From the difference between 
this weight and the total weight before heating, the percentage of 
loss on the amount of material taken is calculated. 

The general appearance of the residue should be noted, especially 
with regard to any changes which the material may have undergone. 
Some relative idea of the amount of hardening which has taken place 
may be obtained from the results of a float or penetration test made 
on the residue, as compared with the results of the same test on the 
original sample. It is also frequently desirable to make the specific 
gravity and other tests on the residue for the purpose of identifying 
or ascertaining the character of the base used in the preparation of 
cut-back products. Before any tests are made on the residue, it 
should be melted and thoroughly stirred while cooling. 

USE OF THE VOLATILIZATION TEST. 

The volatilization test, as above described, is made on practically 
all bitumens with the exception of tars, for which the distillation test 
answers a similar purpose. The test is also frequently made at 105° 
C. for five hours, and with products containing small amounts of water 
it is usually necessary to make a test at the lower temperature before 
the material can be heated at 163° C. without foaming over. In the 
case of emulsions it is customarv to determine the loss on a 20-oram 
sample at room temperature for 24 hours, after which the sample is 
heated at 105° C. for five hours. This additional loss is obtained and 
all determinations are made on the dried residue and reported 
accordingly. 

The volatilization test is also occasionally made at 205° C. for five 
hours on a fresh sample in order to show the effect of this higher 
temperature as compared with the results at 163° C 

DISTILLATION TEST. 

EQUIPMENT. 

1 750 cubic centimeter glass retort with tubulature. 

1 chemical thermometer reading from 0° C. to 400° C. 

6 25 cubic centimeter glass cylinders, graduated to 0.2 cubic centimeter. 

1 iron tripod. 

1 iron support with condenser clamp. 


DISTILLATION TEST. 


25 


1 iron support with burette clamp. 

1 piece of wire gauze, 10 centimeters square. 

2 Bunsen burners. 

1 asbestos hood. (Fig. 12.) 

1 pint tin cup, seamless. 

1 rough balance, capacity 1 kilogram, sensitive to 0.1 gram. 

1 analytical balance, capacity 100 grams, sensitive to 0.1 milligram. 


METHOD. 




'ZD 


Fig. 12.—Asbestos hood for retort. 


Briefly described, this test consists in distilling 250 cubic centimeters 
of the material under examination in a 750-cubic-centimeter glass 
retort at a uniform rate of from 40 to 60 drops per minute and collecting 
the various fractions in weighed 
glass graduates. In preparing for 
the test it will be found convenient 
to mark permanently on the foot of 
each graduate its weight to within 
0.1 gram. Owing to the possibility 
of varying results due to lack of 
uniformity in the retorts, the Office 
of Public Hoads specifies in pur¬ 
chasing that “the retorts shall be 
of such uniform size that, when 
placed in a vertical position with the bulb and mouth of stem resting 
on a level surface, it shall require not less than 725 nor more than 
800 cubic centimeters to cause an overflow into the stem.” 

The retort should be supported with the tubulature in a vertical 
position on one pan of the rough balance and its tare accurately 
obtained. 

From the specific gravity of the tar taken at 25° C., the weight of 
250 cubic centimeters is calculated, and this amount, after warming 
it in a tin cup, if necessary, to make it sufficiently fluid, is poured into 
the tared retort. A cork stopper carrying a thermometer is then 
inserted in the tubulature so that the top of the bulb 1 is level with the 
bottom of the juncture of the stem and the body of the retort, and 
the entire apparatus is set up as shown in figure 13. A cold, wet towel 
wrapped about the stem of the retort may be made to serve as a con¬ 
denser for the lighter distillates. The tar should be heated gradually 
by means of a Bunsen burner and, if it is a crude material containing 
much water, great care must be taken to prevent it from foaming over. 
When the thermometer registers 110° C., the graduated cylinder 


i It was formerly the practice to place the bottom of the bulb level with the bottom of the juncture of 
the stem and body of the retort, and distillation was stopped at 270° C. Recent comparative tests have, 
however, shown that the method now adopted gives results which conform more closely to those obtained 
by the other principal methods in use. As compared with the former method, it may be stated that the 
amount of total distillate to 315° C. is approximately the same as that obtained to 270° C. by the old method. 
The adoption of a standard method of distillation is at present being considered by a special committee 
of the American Society for Testing Materials, and indications point to the fact that considerable research 
will be required both with regard to the type of distilling apparatus, and the standardization of the ther¬ 
mometer and method of distillation before a satisfactory standard can be recommended. 






























26 EXAMINATION OF BITUMINOUS ROAD MATERIALS. 

containing the first fraction is replaced by another, the towel is 
removed, and the asbestos hood placed over the retort to prevent 
radiation and insure a more uniform temperature. The distillation 
should now proceed without difficulty, and the rate should be main¬ 
tained at from 40 to 60 drops per minute. The receiver is changed 
again at 170° C., after melting down by gentle heating any solid 
material that may have been deposited in the stem of the retort. The 
next fraction is collected up to 270° C., using as many graduated 
cylinders as may be necessary without allowing any to become filled 
above the 25 cubic centimeter mark. The last fraction is collected 

up to 315° C., after 
which the burner is 
removed, and any 
solid matter in the 
retort stem is melted 
and collected in the 
last cylinder. 

Any solid matter 
adhering to the sides 
of the graduates is 
melted down by 
playing the flame of 
a burner upon them, 
after which the re- 

Fig. 13. —Distillation apparatus. . . 

tort and graduates 

are cooled to room temperature and their contents determined by 
volume and weight. The volume of pitch remaining in the retort 
is found by deducting the total volume of the distillates from the 
original 250 cubic centimeters taken. If water was present in the 
tar, it will be noticed that the first fraction separates into two lay¬ 
ers, the lower of ammoniacal liquor or water and the upper of oil. 
Note should be made of the approximate volume of solids which 
precipitate from the distillates upon cooling. 

The results obtained are calculated in percentages by volume and 
weight to tenths of 1 per cent and reported as follows: 


Distillate. 


1. Water or ammoniacal liquor. 

2. First light oils to 110° C. 

3. Second light oils 110° C. to 170° C 

4. Heavy oils 170° C. to 270° C. 

5. Heavy oils 270° C. to 315° C.. 

6. Pitch residue.. 


USE OF THE DISTILLATION TEST. 

The distillation test is made upon tars and tar products, but seldom 
upon other materials unless the presence of tar is suspected, or where 


Per cent, Per cent, 
by volume. by weight. 





























DETERMINATION OF BITUMEN SOLUBLE IN CARBON DISULPHIDE. 27 


a determination of water is required. In making the water deter¬ 
mination on viscous or semisolid bituminous materials, it is usually 
advisable to render the samples fluid by the addition of kerosene or 
benzol before attempting the distillation. 


DETERMINATION OF BITUMEN SOLUBLE IN CARBON 

DISULPHIDE. 


EQUIPMENT. 

1 100 cubic centimeter Erlenmeyer flask. 

1 500 cubic centimeter flask with side neck for filtering under pressure. 

1 rubber stopper with one hole. 

1 filter tube, 3.9 centimeters, inside diameter. 

1 platinum Gooch crucible. 

1 piece of seamless rubber tubing, about 3 centimeters in diameter and 3 centimeters 

long. 

50 grams of long fiber amphibole asbestos. 

2 wash bottles; 1 for solvent, 1 for water. 

1 Bunsen burner. 

1 platinum triangle. 

1 iron tripod. 

1 drying oven. 

1 desiccator with calcium chloride. 

1 thermometer reading from —10° C. to 110° C. 

1 vacuum pump and connections. 

1 analytical balance, capacity 100 grams, sensitive to 0.1 milligram. 


METHOD. 


d -— 


6 — 


This test consists in dissolving the bitumen in carbon disulphide 
and recovering any insoluble matter by filtering the solution through 
an asbestos felt. The form of Gooch 
crucible best adapted for the determi¬ 
nation is 4.4 centimeters wide at the 
top, tapering to 3.6 centimeters at 
the bottom, and is 2.5 centimeters 
deep. 

For preparing the felt the necessary 
apparatus is arranged as shown in figure 
14, in which a is the filtering flask, b a 
rubber stopper, c the filter tube, and d a 
section of rubber tubing which tightly 
clasps the Gooch crucible e. The 
asbestos is cut with scissors into pieces 
not exceeding 1 centimeter in length, 
after which it is shaken up with just 
sufficient water to pour easily. The 
crucible is filled with the, suspended 
asbestos, which is allowed to settle for 



Fig. 14.—Apparatus for determining solu¬ 
ble bitumen. 


a 


few moments. A 
light suction is then applied to draw off all the water and leave a 













28 


EXAMINATION OF BITUMINOUS ROAD MATERIALS. 


firm mat of asbestos in the crucible. More of the suspended mate¬ 
rial is added, and the operation is repeated until the felt is so dense 
that it scarcely transmits light when held so that the bottom of the 
crucible is between the eye and the source of light. The felt should 
then be washed several times with water, and drawn firmly against 
the bottom of the crucible by an increased suction. The crucible is 
removed to a drying oven for a few minutes, after which it is ignited 
at red heat over a Bunsen burner, cooled in a desiccator and weighed. 

From 2 to 3 grams of bitumen or about 10 grams of an asphalt 
topping or rock asphalt is now placed in the Erlenmeyer flask, 
which has been weighed previously, and the accurate weight of the 
sample is obtained. One hundred cubic centimeters of chemically 
pure carbon disulphide is poured into the flask in small portions, with 
continual agitation, until all lumps disappear and nothing adheres 
to the bottom. The flask is then corked and set aside for 15 minutes. 

After being weighed, the Gooch crucible containing the felt is 
set up over the dry pressure flask, as shown in figure 14, and the 
solution of bitumen in carbon disulphide is decanted through the felt 
without suction by gradually tilting the flask, with care not to stir 
up any precipitate that may have settled out. At the first sign of 
any sediment coming out, the decantation is stopped and the filter 
allowed to drain. A small amount of carbon disulphide is then 
washed down the sides of the flask, after which the precipitate is 
brought upon the felt and the flask scrubbed, if necessary, with a 
feather or “policeman,” to remove all adhering material. The con¬ 
tents of the crucible are washed with carbon disulphide, until the 
washings run colorless. Suction is then applied until there is prac¬ 
tically no odor of carbon disulphide in the crucible, after which the 
outside of the crucible is cleaned with a small amount of the solvent. 
The crucible and contents are dried in the hot-air oven at 100° C. 
for about 20 minutes, cooled in a desiccator, and weighed. If any 
appreciable amount of insoluble matter adheres to the flask, it 
should also be dried and weighed, and any increase over the original 
weight of the flask should be added to the weight of insoluble matter 
in the crucible. The total weight of insoluble material may include 
both organic and mineral matter. The former, if present, is burned 
off by ignition at a red heat until no incandescent particles remain, 
thus leaving the mineral matter or ash, which can be weighed on 
cooling. The difference between the total weight of material insolu¬ 
ble in carbon disulphide and the weight of substance taken equals 
the total bitumen, and the percentage weights are calculated and 
reported as total bitumen, and organic and inorganic matter insolu¬ 
ble, on the basis of the weight of material taken for analysis. 

This method is quite satisfactory for straight oil and tar products, 
but where natural asphalts are present it will be found practically 


DETERMINATION OF BITUMEN SOLUBLE IN CARBON DISULPHIDE. 29 


impossible to retain all of the finely divided mineral matter on an 
asbestos felt. It is, therefore, generally more accurate to obtain the 
result for total mineral matter by direct ignition of a 1-gram sample 
in a platinum crucible or to use the result for ash obtained in the 
fixed carbon test. The total bitumen is then determined by deduct¬ 
ing from 100 per cent the sum of the percentages of total mineral 
matter and organic matter insoluble. If the presence of a carbonate 
mineral is suspected, the percentage of mineral matter may be most 
accurately obtained by treating the ash from the fixed carbon deter¬ 
mination with a few drops of ammonium carbonate solution, drying at 
100° C., then heating for a few minutes at a dull red heat, cooling, 
and weighing again. 

When difficulty in filtering is experienced—for instance, when Trini¬ 
dad asphalt is present in any amount—a period of longer subsidence 
than 15 minutes is necessary, and the following method proposed by 
the committee on standard tests for toad materials of the American 
Society for Testing Materials is recommended: 

From 2 to 15 grams (depending on the richness in bitumen of the substance) is 
weighed into a 150-cubic centimeter Erlenmeyer flask, the tare of which has been 
previously ascertained , and treated with 100 cubic centimeters of carbon disulphide. 
The flask is then loosely corked and shaken from time to time until practically all 
large particles of the material have been broken up, when it is set aside and not dis¬ 
turbed for 48 horns. The solution is then decanted off into a similar flask that has 
been previously weighed, as much of the solvent being poured off as possible without 
disturbing the residue. The first flask is again treated with fresh carbon disulphide 
and shaken as before, when it is put away with the second flask and not disturbed for 
48 hours. 

At the end of this time the contents of the two flasks are carefully decanted off 
upon a weighed Gooch crucible fitted with an asbestos filter, the contents of the sec¬ 
ond flask being passed through the filter first. The asbestos filter shall be made of 
ignited long-fiber amphibole, packed in the bottom of a Gooch crucible to the depth 
of not over one-eighth of an inch. After passing the contents of both flasks through 
the filter, the two residues are shaken with more fresh carbon disulphide and set aside 
for 24 hours without disturbing, or until it is seen that a good subsidation has taken 
place, when the solvent is again decanted off upon the filter. This washing is con¬ 
tinued until the filtrate or washings are practically colorless. 

The crucible and both flasks are then dried at 125° C. and weighed. The filtrate 
containing the bitumen is evaporated, the bituminous residue burned, and the 
weight of the ash thus obtained added to that of the residue in the two flasks and the 
crucible. The sum of these weights deducted from the weight of substance taken 
gives the weight of bitumen extracted. 

O o 

USE OF TOTAL BITUMEN DETERMINATION. 

This determination is made on all classes of bituminous products. 
In the analysis of tars the organic matter insoluble is commonly 
known and reported as “free carbon. 


i Proc. Am. Soc. for Testing Materials, 1909, Vol. IX, p. 221. 





30 


EXAMINATION OF BITUMINOUS ROAD MATERIALS. 


DETERMINATION OF BITUMEN INSOLUBLE IN PARAFFIN 

NAPHTHA. 

EQUIPMENT. 

The apparatus is the same as for bitumen soluble in carbon disulphide. 

METHOD. 

This determination is made in the same general manner as the 
total bitumen determination, except that 100 cubic centimeters of 
86° B. paraffin naphtha is employed as a solvent instead of carbon 
disulphide. Considerable difficulty is sometimes experienced in 
breaking up some of the heavy semisolid bitumens; the surface of the 
material is attacked, but it is necessary to remove some of the 
insoluble matter in order to expose fresh material to the action of 
the solvent. It is, therefore, advisable to heat the sample after it is 
weighed, allowing it to cool in a thin layer around the lower part of 
the flask. If difliculty is still experienced in dissolving the material, 
a rounded glass rod will be found convenient for breaking up the 
undissolved particles. Not more than one-half of the total amount 
of naphtha required should be used until the sample is entirely 
broken up. The balance of the 100 cubic centimeters is then added, 
and the flask is twirled a moment in order to mix the contents thor¬ 
oughly, after which it is corked and set aside for 30 minutes. 

In making the filtration the utmost care should be exercised to 
avoid stirring up any of the precipitate, in order that the filter may 
not be clogged and that the first decantation may be as complete as 
possible. The sides of the flask should then be quickly washed down 
with naphtha and, when the crucible has drained, the bulk of insoluble 
matter is brought upon the felt. Suction may be applied when the 
filtration by gravity almost ceases, but should be used sparingly, as 
it tends to clog the filter by packing the precipitate too tightly. The 
material on the felt should never be allowed to run entirely dry until 
the washing is completed, as shown by the colorless filtrate. When 
considerable insoluble matter adheres to the flask, no attempt should 
be made to remove it completely. In such cases the adhering mate¬ 
rial is merely washed until free from soluble matter, and the flask is 
dried with the crucible at 100° C. for about one hour, after which it 
is cooled and weighed. The percentage of bitumen insoluble is 
reported upon the basis of total bitumen taken as 100. 

The difference between the material insoluble in carbon disulphide 
and in the naphtha is the bitumen insoluble in the latter. Thus, if 
in a certain instance it is found that the material insoluble in carbon 
disulphide amounts to 1 per cent and that 10.9 per cent is insoluble 
in naphtha, the percentage of bitumen insoluble would be calculated 
as follows: 

Bitumen inso luble in naphtha 10.9 — 1 9.9 

Total bitumen — 100 — 1 ~ 99 ~ ^ P er cen ^- 






BITUMEN INSOLUBLE IN CARBON TETRACHLORIDE. 31 

USE OF NAPHTHA INSOLUBLE BITUMEN DETERMINATION. 

This test is made on all petroleums, malthas, asphalts, and other 1 
solid native bitumens and their products. 

It should be noted that petroleum naphthas are by no means defi¬ 
nite compounds, but are composed of a number of hydrocarbons 
which vary in character and quantity according to the petroleum 
from which they have been distilled. Their solvent powers also vary 
greatly. Thus naphthas produced from asphaltic petroleums, con¬ 
sisting mainly of naphthene and polymethylene hydrocarbons, are 
much more powerful solvents of the heavier asphaltic hydrocarbons 
than are the paraffin naphthas. The density of the naphtha also 
affects its solvent power, for those of high specific gravity dissolve the 
heavier hydrocarbons more readily than those of lower specific grav¬ 
ity. As the main object of this test is to separate the heavier hydro¬ 
carbons of an asphaltic nature from the paraffin hydrocarbons, a 
paraffin solvent should be employed, and for ordinary purposes a 
paraffin naphtha of 86° B. gravity, distilling between 40° C. and 65° C., 
has been found to be readily obtainable and fairly satisfactory. The 
solvent action of 88° B. naphtha is a little lower, and therefore prefer¬ 
able, but it can not be as readily obtained. 

The determination is also frequently made with heavier naphthas, 
such as 66° B. and 72° B., for the purpose of grading the character 
of the bitumen present in the compound. A report should therefore 

always distinctly state the gravity and character of the solvent used. 

» 

DETERMINATION OF BITUMEN INSOLUBLE IN CARBON TETRA¬ 
CHLORIDE. 

EQUIPMENT. 

The apparatus is the same as for bitumen soluble in carbon disulphide. 

METHOD. 

This determination is conducted in exactly the same manner as 
described under “ Determination of bitumen soluble in carbon disul¬ 
phide,” using 100 cubic centimeters of chemically pure carbon 
tetrachloride in place of carbon disulphide. 

The percentage of bitumen insoluble is reported upon the basis 
of total bitumen taken as 100, as described under “Determination of 
bitumen insoluble in paraffin naphtha.” 

USE OF DETERMINATION OF BITUMEN INSOLUBLE IN CARBON 

TETRACHLORIDE. 

The bitumen insoluble in carbon tetrachloride, but soluble in car¬ 
bon disulphide, is commonly known as “carbenes.” The test is 
occasionally made on petroleums, asphalts, and other solid native 


32 


EXAMINATION OF BITUMINOUS ROAD MATERIALS. 


bitumens and their products, for the purpose of identification, or 
when there is any reason to suspect that the material under exami¬ 
nation has been injured by overheating during the process of manu¬ 
facture. 

DETERMINATION OF FIXED CARBON. 


EQUIPMENT. 

1 iron ring support (ring 7.5 cm. in diameter). 

1 platinum triangle. 

1 Bunsen burner and rubber tubing. 

1 platinum crucible with a tight-fitting cover (weight complete, from 20 to 30 grains). 
1 crucible tongs. 

1 desiccator with calcium chloride. 

1 analytical balance, capacity 100 grams, sensitive to 0.1 milligram. 


METHOD. 


This determination is made in accordance with the method de¬ 
scribed for coal in the Journal of the American Chemical Society, 1899, 

volume 21, page 1116. One gram of the 
material is placed in a platinum crucible 
weighing from 20 to 30 grams and having 
a tightly fitting cover. It is then heated 
for seven minutes over the full flame of a 
Bunsen burner, as shown in figure 15. 
The crucible should be supported on a 
platinum triangle with the bottom from 
6 to 8 centimeters above the top of the 
burner. The flame should be fully 20 
centimeters high when burning freely, and 
the determination should be made in a 
place free from drafts. The upper surface 
of the cover should burn clear, but the 
under surface should remain covered with 
carbon, excepting in the case of some of 
the more fluid bitumens, when the under 
surface of the cover may be quite clean. 

The crucible is removed to a desiccator 
and when cool is weighed, after which the 
cover is removed, and the crucible is placed 
in an inclined position over the Bunsen burner and ignited until noth¬ 
ing but ash remains. Any carbon deposited on the cover is also burned 
off. The weight of ash remaining is deducted from the weight of the 
residue after the first ignition of the sample. This gives the weight 
of the so-called fixed or residual carbon, which is calculated on a basis 



Fig 


15.—Apparatus for determining 
fixed carbon. 































DETERMINATION OF PARAFFIN SCALE. 


33 


of the total weight of the sample, exclusive of mineral matter. If 
the presence of a carbonate mineral is suspected, the percentage 
of mineral matter may be most accurately obtained by treating the 
ash with a few drops of ammonium carbonate solution, drying at 
100° C., then heating for a few minutes at a dull red heat, cooling 
and weighing. 

An excellent form of crucible for this test is shown in figure 15. 
It has a cover with a flange 4 millimeters wide, fitting tightly over 
the outside of the crucible, and weighs complete about 25 grams. 
Owing to sudden expansion in burning some of the more fluid bitu¬ 
mens, it is well to hold the cover down with the end of the tongs 
until the most volatile products have burned off. 

USE OF DETERMINATION FOR FIXED CARBON. 

This determination is made on all bituminous products with the 
exception of tars, upon which reliable results can not be obtained; 
owing to the error introduced by the presence of considerable quan¬ 
tities of free carbon. 

DETERMINATION OF PARAFFIN SCALE. 

EQUIPMENT. 

1 200 cubic centimeter (6 oz.) glass retort (for each determination). 

1 150 cubic centimeter Erlenmeyer flask. 

1 100 cubic centimeter Erlenmeyer flask. 

1 500 cubic centimeter (16 oz.) flask, with side neck for filtering under pressure. 

1 glass funnel 65 millimeters in diameter, stem 150 millimeters long (Fig. 16-a). 

1 freezing mixture reservoir (Fig. 16-6). 

2 rubber stoppers with hole (Figs. 16-c and 16-d). 

1 analytical balance, capacity 100 grams, sensitive to 0.1 milligram. 

1 rough balance, capacity 1 kilogram, sensitive to 0.1 gram. 

1 wash bottle. 

1 quart tin cup, seamless. 

1 package C. S. & S. 9 centimeter hardened filter papers. 

1 vacuum pump and connections. 

1 glass crystallizing dish 50 millimeters in diameter. 

1 steam bath. 

1 desiccator with calcium chloride. 

1 4-inch steel spatula. 

1 Bunsen burner with rubber tubing. 

1 iron stand with retort clamp. 

METHOD. 

One hundred grams of the material under examination should be 
weighed into the tared glass retort and distilled as rapidly as possible 
to dry coke. The distillate is caught in a 150-cubic-centimeter 
Erlenmeyer flask, the weight of which has been previously ascer- 


34 


EXAMINATION OF BITUMINOUS ROAD MATERIALS. 


tained. During the early stages of distillation a cold, damp towel 
wrapped around the stem of the retort will serve to condense the 
distillate. After high temperatures have been reached, this towel 
may be removed. When the distillation is completed, the distillate 
is allowed to cool to room temperature and is then weighed in the 
flask. This weight minus that of the flask gives the weight of the 
total distillate. -**■>' 

Five grams of the well mixed distillate is then weighed into a 
100-cubic-centimeter Erlenmeyer flask and mixed with 25 cubic 
centimeters of Squibb’s ether. Twenty-five cubic centimeters of 
Squibb’s absolute alcohol is then added, after which the flask is 
packed closely in a freezing mixture of finely crushed ice and salt 
maintained at —18° C. in a quart tin cup. After remaining 30 
minutes in this mixture, the solution is quickly filtered through a 

No. 575 C. S. & S. 9-centimeter hard¬ 
ened filter paper placed in a glass fun¬ 
nel, winch is packed in a freezing mix¬ 
ture, as shown in figure 16. Vacuum 
should be employed to hasten filtration. 
The freezing-mixture reservoir shown in 
figure 16-& may be made by cutting in 
half a round glass bottle measuring ap¬ 
proximately 120 millimeters in diameter 
and using the upper half in an inverted 
position. Any precipitate remaining on 
the paper should be washed until free 
from oil with about 50 cubic centimeters 
of a 1 to 1 mixture of Squibb’s ether and 
absolute alcohol cooled to — 18° C. 

After the paper has been sucked dry, 
it should be removed from the funnel 
and the adhering paraffin scale should be scraped off into a weighed 
crystallizing dish and dried on a steam bath. The dish and contents 
should then be cooled in a desiccator and weighed. 

The weight of the paraffin scale so obtained, divided by the weight 
of the distillate taken and multiplied by the percentage of the total 
distillate obtained from the original sample, equals the percentage 
of the paraffin scale. 



Fig. 16.—Apparatus for determining 
paraffin scale. 


USE OF PARAFFIN SCALE DETERMINATION. 

The paraffin scale determination may be made on all native bitu¬ 
mens and their products which are suspected of being of a paraffin 
nature. It is not an extremely accurate determination, however, and 
is seldom employed by the Office of Public Roads. 










THE EXTRACTION OF BITUMINOUS AGGREGATES. 


35 


THE EXTRACTION OF BITUMINOUS AGGREGATES. 

EQUIPMENT FOR RECOVERING AGGREGATE ONLY. 

1 centrifuge extractor, complete with motor, speed regulator, and electrical connec¬ 
tions. (Fig. 17.) 

1 hot plate. 

1 enamel-ware dish approximately 2 inches deep and 9 inches in diameter. 

1 hammer. 

1 three-fourths-inch cold chisel. 

1 large metal kitchen spoon. 

1 square foot of one-sixteenth-inch deadening felt paper. 

1 1^-inch stiff flat brush. 

1 500 cubic centimeter bottle or flask. 

1 balance, capacity 1 kilogram, sensitive to 0.1 gram. 

1 sheet of heavy manila paper. 

ADDITIONAL EQUIPMENT FOR RECOVERING BITUMEN.' 

* 

1 iron ring support (ring 10 centimeters in diameter). 

1 iron ring support with condenser clamp. 

1 round tin can, 10 by 12 centimeters, covered with asbestos paper/ 

1 32-candlepower incandescent lamp, with socket and connections. 

1 asbestos hood. (Fig. 18-c.) 

1 1,000 cubic centimeter round-bottom flask, with cork. 

1 spiral condenser, length of body 25 centimeters, with cork to fit, and rubber-tubing 
connections. 

50 centimeters of glass tubing, 8 millimeters bore? 

1 1,000 cubic centimeter flat-bottom flask. 

1 porcelain evaporating dish, 11 centimeters in diameter^ 

1 watch glass, 20 centimeters in diameter. 

1 steam bath/ 

METHOD. 

The extractor shown in figure 17 was designed upon lines suggested by 
an examination of machines in use by A. E. Schutte and C. N. Forrest. 
It consists of a one-fifth-horsepower 1,100 revolutions per minute ver¬ 
tical-shaft electric motor a, with the shaft projecting into the cylin¬ 
drical copper box b, the bottom of which is so inclined as to drain to 
the spout c. A three-sixteenths-inch circular brass plate 9J inches 
in diameter is shown in d, and upon this rests the sheet-iron bowl e, 
which is 8 J inches in diameter by 2/§- inches high, and has a 2-inch cir¬ 
cular hole in the top. Fastened to the inner side of the bowl is the 
brass cup/, having a circle of one-eighth-inch holes for the admission 
of the solvent, and terminating in the hollow axle, which fits snugly 
through a hole at the center of the brass plate. The bowl may be 
drawn firmly against a felt-paper ring g, three-fourths inch wide, by 
means of the 2J-inch milled nut h, for which the hollow axle is 
threaded for a distance of three-fourths inch directly below the upper 
surface of the plate. The axle fits snugly over the shaft of the motor, 
to which it is locked by a slot and cross pin i. 


36 


examination of bituminous road materials. 



—c 


The aggregate is prepared for analysis by heating it in an enamel-ware 
pan on the hot plate until it is sufficiently soft to be thoroughly dis¬ 
integrated by means of a large spoon. Care must be taken, however, 
that the individual particles are not crushed. If a section of pave¬ 
ment is under examination, a piece weighing somewhat over 1 kilogram 
may be cut off with hammer and chisel. The disintegrated aggregate 
is then allowed to cool, after which a sufficient amount is taken to 
yield-on extraction from 50 to 60 grams of bitumen. It is placed in 
the iron bowl and a ring three-fourths of an inch wide, cut from the 
felt paper, is fitted on the rim, after which the brass plate is placed 
in position and drawn down tightly by means of the milled nut. If 

the bitumen is to be recovered and 
examined, the felt ring should be 
previously treated in the empty ex¬ 
tractor with a couple of charges of 
carbon disulphide in order to remove 
any small amount of grease or resin 
that may be present, although a proper 
grade of felt should be practically free 
from such products. The bowl is now 
placed on the motor shaft and the 
slot and pin are carefully locked. An 
empty bottle is placed under the spout 
and 150 cubic centimeters of carbon 
disulphide is poured into the bowl 
through the small holes. The cover 
is put on the copper box and, after 
allowing the material to digest for a 
few minutes, the motor is started, 
slowly at first in order to permit the 
aggregate to distribute uniformly. 
The speed should then be increased sufficiently by means of the 
regulator to cause the dissolved bitumen to flow from the spout in 
a thin stream. When the first charge has drained, the motor is 
stopped and a fresh portion of disulphide is added. This operation 
is repeated from four to six times with 150 cubic centimeters of 
disulphide. With a little experience the operator can soon gauge 
exactly what treatment is necessary for any given material. When 
the last addition of solvent has drained off, the bowl is removed 
and placed with the brass plate uppermost on a sheet of manila 
paper. The brass plate and felt ring are carefully laid aside on the 
paper and, wlien the aggregate is thoroughly dry, it can be brushed 
on a pan of the rough balance and weighed. The difference between 



Fig. 17.—Office of Public Roads centrifuge ex 
tractor (Reeve type). 






























THE EXTRACTION OF BITUMINOUS AGGREGATES. 


37 


this weight and the original weight taken shows the amount of bitumen 
extracted. The aggregate may then be tested as occasion requires. 

When it is desired to recover and examine the bitumen, the appa¬ 
ratus shown in figure 18 will be found convenient and fairly safe for the 
distillation and recovery of such inflammable solvents as carbon 
disulphide. In the laboratory of the Office of Public Roads this 
apparatus is arranged so that the glass tubing passes through a stone 
partition between two sections of a small hood, thus keeping the 
distilling and receiving apparatus entirely separated. 

The solution of bitumen should be allowed to stand overnight in 
order to permit the settling of any fine mineral matter that is some¬ 
times carried through 
the felt ring in the 
extractor. The solu¬ 
tion is then decanted 
into the flask a, and 
the solvent is driven 
off by means of heat 
from an incandescent 
lamp until the residue 
is of a thick sirupy 
consistency. Mean¬ 
while the solvent is 
condensed and recov¬ 
ered in the flask b. 

The residue is poured 
into an 11 -centime ter 
porcelain evaporating 
dish, and evaporated 
on a steam bath. 

Fig. 18—Recovery apparatus. 

The most scrupulous 

care must be taken at all times that no flames are in its immediate 
vicinity. Evaporation is carried on at a gentle heat, with con¬ 
tinual stirring, until foaming practically ceases. It is advisable 
to have a large watch glass at hand to smother the flames quickly, 
should the material ignite. As the foaming subsides, the heat of the 
steam bath may be gradually raised, and evaporation is continued 
until the bubbles beaten or stirred to the surface of the bitumen fail 
to give a blue flame or odor of sulphur dioxide when ignited by a small 
gas jet. The dish of bitumen should then be set in a hot-air oven 
maintained at 105° C. for about an hour, after which it is allowed to 
cool. Its general character is noted and any tests for bitumens that 
are necessary are then made upon it. 














































38 


EXAMINATION OF BITUMINOUS HOAD MATEKIALS. 


GRADING THE MINERAL AGGREGATE. 

EQUIPMENT. . 

1 set of 18-inch stone sieves with meshes of 1|, lj, 1, f, I, and finches, respectively. 
1 set of 8-inch brass sand sieves of 10, 20, 30,40, 50, 80,100, and 200 mesh, respectively, 
with pan and cover. 

1 rough balance, capacity 1 kilogram, sensitive to 0.1 gram. 

1 1^-inch stiff flat brush. 

Several sheets of manila paper. 

METHOD. 

For aggregates containing particles too large to pass a one-eighth- 
inch screen, the stone sieves are used, and are stacked in their regular 
order over a sheet of heavy paper, with the largest size required on top. 
The weighed amount of stone is placed on the largest sieve and is care¬ 
fully protected from drafts which might carry away any of the fine 
material. The upper sieve is then removed from the stack and shaken 
over a large sheet of paper until no more particles come through. 
The material thus retained, including any fragments caught in the 
meshes of the sieve, is weighed and that which passes is added to the 
contents of the succeeding sieve. This operation is repeated with 
each succeeding sieve. 

When grading sands or fine aggregates, it is customary to take a 
100-gram sample in order that the weights may give direct percentages 
to tenths of 1 per cent. The sieves are stacked in regular order with 
the 200-mesh sieve resting on the pan. The sample is brushed on the 
top sieve, after which the cover is put on and the stack agitated for 
about five minutes with both rocking and circular shaking. Each sieve 
is removed in order, and shaken and tapped on a clean piece of paper 
until no appreciable amount of material comes through. All lumps 
are broken up by crushing them against the side of the sieve with the 
finger or a small spatula. The contents of the sieve are emptied into 
the pan of the balance. All particles caught in the mesh are removed 
by brushing across the underside of the sieve and are added to the 
contents of the pan. As great opportunity exists for wide variations 
in the results of sand gradings made by different persons, owing to 
the possibility of always getting a little more material to pass by 
continued shaking, it is well for the novice to repeat his sifting on 
any given mesh, after having weighed it, in order to see what fur¬ 
ther loss he can produce. If his judgment has not erred, several 
minutes’ further sifting should not produce a loss of over 0.5 gram. 

Where coarse aggregates have considerable material passing a one- 
eighth-inch screen and it is desired to grade this material further, it 
should be weighed and well mixed, quartered, if necessary, and a 
100-gram sample should be passed through the sand sieves. From 
the percentages so obtained and the weight of material passing the 


DETERMINATION OF VOIDS IN THE MINERAL AGGREGATE. 39 


one-eiglith-inch sieve, the percentages of the total aggregate which 
these finer materials represent may be calculated. 

The Office of Public Roads has adopted the following recommen¬ 
dations of the committee on standard tests for road materials of the 
American Society for Testing Materials as to the size of wire for 
standard sand sieves: 


Diameter 


Meshes per linear inch: niches.’ 

10.0.027 

20.0165 

30.01375 

40.01025 


Diameter 


. of wire, 

Meshes per linear inch: inches. 

50. 0.009 

80.00575 

100.0045 

200.00235 


DETERMINATION OF VOIDS IN THE MINERAL AGGREGATE. 


EQUIPMENT. 

1 section of 4-inch steel pipe, machined on the inside and cut to such a length that its 
cubical contents equal 1,000 cubic centimeters. 

1 2,000 cubic centimeter graduated glass cylinder. 

1 10-inch trowel. 

1 small tin scoop. 

1 H-inch stiff flat brush. 

1 2-foot length of metal rod. 

• 2 sheets of manila paper. 

METHOD. 

The aggregate is thoroughly mixed, and quartered, if necessary, 
until a representative sample of material more than sufficient to fill 
the section of pipe is obtained. The pipe is set upright on a sheet 
of manila paper and the aggregate poured in, a scoopful at a time, 
and tamped continuously with the trowel handle. Care must be 
taken that no segregation of the material occurs, either in scooping 
up or pouring it into the pipe. The pipe is filled “level full,” or 
approximately so, if the aggregate gives an uneven surface, after 
which it is raised and the contents, which equal 1,000 cubic centi¬ 
meters, are allowed to remain in a pile on the paper. 

About 600 cubic centimeters of water is placed in the glass cylinder 
and an accurate reading of the volume is taken; this is called “a.” 
The measured quantity of the aggregate is now poured in, a little at 
a time, and stirred with the metal rod to displace any air bubbles. 
When all has been added and the dust has settled sufficiently to give 
a clear meniscus, the volume is again read and this reading is called 
“b.” The percentage of voids may then be calculated from the 
following formula: 

-r, , t i 1000—(b —a) X100 1000 —b + a 

Percentage ol voids =-fOOC)-° r -10-* 












APPENDIX. 


LABORATORY EQUIPMENT. 

The necessary equipment for a small laboratory about to engage in 
the routine testing and inspection of bitumens is given in the following 
list. The maximum cost, exclusive of platinum ware, solvents, and 
chemicals, should not exceed $300, and the material could no doubt 
be purchased at a lower figure by securing bids on the entire equip¬ 
ment from several of the chemical supply houses. 

For the extraction of bituminous aggregates, the recovery of the 
bitumen, and examination of the aggregates, the additional equip¬ 
ment described for that work will be required at an additional cost of 
approximately $125. 

APPARATUS. • 

1 analytical balance, capacity 100 grams, sensitive to 0.1 milligram. 

1 set of weights, 50 grams to 5 milligrams, with rider. 

1 rough balance, capacity 1 kilogram, sensitive to 0.1 gram. 

1 stop watch. 

1 Engler viscosimeter. 

1 penetrometer. 

1 New York State Board of Health oil tester. 

1 aluminum float with 3 brass collars. 

1 cubical brass mold. 

1 brass plate 5 by 8 centimeters. 

1 metal cover for melting point apparatus. 

1 constant temperature oven. 

1 thermo-regulator. 

1 hot plate 14 by 18 inches. 

1 steam bath. 

1 small drying oven. 

6 Bunsen burners. 

4 iron tripods. 

4 iron ring supports. 

3 rings for ring support, 7.5 centimeters in diameter. 

3 condenser clamps. 

3 burette clamps. 

6 pieces of wire gauze, 10 by 10 centimeters. 

2 enamel-ware dishes, 3 inches deep by 9 inches in diameter. 

6 1-pint tin cups, seamless. 

6 1-quart tin cups, seamless. 

12 tin boxes, 6 centimeters in diameter by 2 centimeters deep. 

6 tin boxes, 5 centimeters in diameter by 3.5 centimeters deep. 

1 metal kitchen spoon. 

40 


APPENDIX. 


41 


110-centimeter steel spatula. 

1 crucible tongs. 

1 hammer. 

1 f-inch cold chisel. 

1 li-inch stiff flat brush. 

1 triangular file. 

1 small round file. 

1 set of cork borers, Nos. 1 to 12. 

1 brass filter (vacuum) pump. 

1 piece of wire, 20 centimeters long (No. 12 Brown & Sharpe gauge). 

3 chemical thermometers reading from —10° 0. to 110° C. 

3 chemical thermometers reading from 0° C. to 250° C. 

2 chemical thermometers reading from 0° C. to 400° C. 

4 hydrometers, 0.800 to 0.900; 0.900 to 1.000; 1.000 to 1.200; 1.200 to 1.400. 

1 hydrometer jar, 350 by 50 millimeters. 

1 special pycnometer. 

6 250 cubic centimeter beakers, low form. 

G 150 cubic centimeter beakers, low form. 

2 800 cubic centimeter beakers, low form. 

2 400 cubic centimeter beakers, tall form, without lip. 

1 10-centimeter crystallizing dish, deep, straight sides. 

1 5-centimeter crystallizing dish. 

12 100 cubic centimeter Erlenmeyer flasks. 

2 150 cubic centimeter Erlenmeyer flasks. 

2 500 cubic centimeter flasks with side neck for filtering under pressure. 

6 750 cubic centimeter glass retorts, with tubulature. 

6 200 cubic centimeter glass retorts, with tubulature. 

4 500 cubic centimeter wash bottles, with tubulated glass stopper ground into neck, 

for solvents. 

1 1,000 cubic centimeter wash bottle for water. 

6 100 cubic centimeter glass cylinders, graduated to 1 cubic centimeter. 

6 25 cubic centimeter glass cylinders, graduated to 0.2 cubic centimeter. 

1 150-millimeter desiccator with porcelain plate. 

1 filter tube for Gooch crucible 3.9 centimeters in diameter. 

1 object glass. 

1 pound of light glass tubing, assorted. 

1 pound of glass rods, assorted. 

2 rubber stoppers, No. 8, with one hole. 

2 rubber stoppers, No. 1, with one hole. 

5 pounds of rubber gas tubing, d inch internal diameter. 

1 foot of rubber tubing, 1 inch diameter, for Gooch crucibles. 

5 pounds of heavy asbestos paper. 

Corks, assorted. 

PLATINUM. 

1 triangle, 5 centimeter sides (10 to 12 grams). 

1 Gooch crucible, as specified (20 to 25 grams) for solubility determinations. 

1 crucible with tight fitting, flanged lid (about 25 grams) for fixed carbon determina¬ 
tions. 

SOLVENTS AND CHEMICALS. 

Carbon disulphide, chemically pure. 

86° Baume paraffin naphtha, distilling between 40° C. and 65° C. 

Carbon tetrachloride, chemically pure. 

Ether (Squibb’s). 

Alcohol, absolute (Squibb’e). 


42 


EXAMINATION OF BITUMINOUS ROAD MATERIALS 


Cottonseed oil. 

Mercuric chloride or nitrate. 

Mercury. 

Ammonium carbonate, chemically pure. 
Calcium chloride, granular for desiccator. 
Asbestos, pure long fiber amphibole. 

C. S. & S. 9-centimeter hardened filter papers. 


Metric conversion tables. 


Length. 

Inches. 

Millimeters. 

&=0.0312 

0.7938 

• 0625 

1.5875 

&= .1250 

3.1750 

i= .2500 

6.3500 

£= .5000 

12. 7000 

1. 

25. 4001 

2. 

50. 8001 

3. 

76. 2002 

4. 

101. 6002 

5. 

127.0003 

6. 

152. 4003 

7. 

177. 8004 

8. 

203.2004 

9. 

228. 6005 

Centi¬ 

meters. 

0.3937 

1=10 mm. 

.7874 

2 

1.1811 

3 

1.5748 

4 

1.9685 

5 

2.3622 

6 

2.7559 

7 

3.1496 

8 

3.5433 

9 


Capacity. 


Mass. 

United States 

Cubic centi- 

Avoirdupois 

Grams. 

liquid ounces. 

meters. 

ounces. 

1. 

29.574 

1. 

28. 3495 

2. 

59.147 

2. 

56. 6991 

3. 

88. 721 

3. 

85. 0486 

4. 

118. 295 

4. 

113. 3981 

5. 

147. 869 

5. 

141. 7476 

6. 

177. 442 

6. 

170. 0972 

7. 

207. 016 

7. 

198. 4467 

8. 

236.590 

8. 

226. 7962 

9. 

266.163 

9. 

255.1457 

16=1 pt... 

473.18 

16=1 lb.... 

453.59 

32=1 qt... 

946. 36 

0. 3527. 

10 

128=1 gal... 

3,785.43 

.7055 

20 

0.3381. 

10 

1.0582. 

30 

.6763. 

20 

1.4110. 

40 

1.0144. 

30 

1.7637. 

50 

1.3526. 

40 

2.1164. 

> 60 

1.6907. 

50 

2. 4692. 

70 

2.0288. 

60 

2.8219. 

80 

2.3670. 

70 

3.1747. 

90 

2.7051. 

80 

3. 5270. 

100 

3.0432. 

3.3810. 

33.81. 

90 

100 

1,000=1 

liter. 

35.27. 

1,000= 1 kilogram. 


Comparison of Degrees Baume and Specific Gravity. 
(Liquids lighter than water.) 


(1) Sp. gr. 


140 

I30+°B. 


at 15.5° C. 


(2) °B. 


140 

Sp. gr. 


130 at 15.5° C. 


°B. 

Sp. Gr. 

°B. 

Sp. Gr. 

°B. 

Sp. Gr. 

°B. 

Sp. Gr. 

10 

1.0000 

31 

0.8695 

52 

0.7692 

73 

0.6896 

11 

.9929 

32 

.8641 

53 

.7650 

74 

.6863 

12 

.9859 

33 

.8588 

54 

.7609 

75 

.6829 

13 

.9790 

34 

.8536 

55 

.7567 

76 

. 6796 

14 

.9722 

35 

.8484 

56 

.7526 

77 

.6763 

15 

.9655 

36 

.8433 

57 

.7486 

78 

.6731 

16 

.9589 

37 

.8383 

58 

.7446 

79 

.6698 

17 

.9523 

38 

.8333 

59 

.7407 

80 

.6666 

18 

.9459 

39 

.8284 

60 

.7368 

81 

.6635 

19 

.9395 

40 

.8235 

61 

.7330 

82 

.6604 

20 

.9333 

41 

.8187 

62 

.7292 

83 

.6573 

21 

.9271 

42 

.8139 

63 

.7254 

84 

.6542 

22 

.9210 

43 

.8092 

64 

.7216 

85 

.6511 

23 

.9150 

44 

.8045 

65 

.7179 

86 

.6482 

24 

.9090 

45 

.8000 

66 

.7143 

87 

.6452 

25 

.9032 

46 

.7954 

67 

.7107 

88 

.6422 

26 

.8974 

47 

.7909 

68 

.7071 

89 

.6393 

27 

.8917 

48 

.7865 

69 

.7035 

90 

.6363 

28 

.8860 

49 

.7821 

70 

.7000 



29 

.8805 

50 

.7777 

71 

.6965 



30 

.8750 

51 

.7734 

72 

.6931 






























































































APPENDIX 


43 


Comparison of Centigrade and Fahrenheit degrees. 
(1) °F.=|- 0 C.+32. (2) 0 C.= 5 -(° F 9 ~ 32 l 


c. 

F. 

C. 

F. 

C. 

F. 

C. 

F. 

C. 

F. 

C. 

F. 

0 

32.0 

38 

100.4 

76 

168.8 

114 

237.2 

152 

305.6 

190 

374.0 

1 

33.8 

39 

102.2 

77 

170.6 

115 

239.0 

153 

307.4 

191 

375.8 

2 

35.6 

40 

104.0 

78 

172.4 

116 

240.8 

154 

309.2 

192 

377.6 

3 

37.4 

41 

105.8 

79 

174.2 

117 

242.6 

155 

311.0 

193 

379.4 

4 

39.2 

42 

107.6 

80 

176.0 

118 

244.4 

156 

312.8 

194 

381.2 

5 

41.0 

43 

109.4 

81 

177.8 

119 

246.2 

157 

314.6 

195 

383.0 

0 

42.8 

44 

111.2 

82 

179.6 

120 

248.0 

158 

316.4 

196 

384.8 

7 

44.6 

45 

113.0 

83 

181.4 

121 

249.8 

159 

318.2 

197 

386.6 

8 

46.4 

46 

114.8 

84 

183.2 

122 

251.6 

160 

320.0 

198 

388.4 

9 

48.2 

47 

116.6 

85 

185.0 

123 

253.4 

161 

321.8 

199 

390.2 

10 

50.0 

48 

118.4 

86 

186.8 

124 

255.2 

162 

323.6 

200 

392.0 

11 

51.8 

49 

120.2 

87 

188.6 

125 

257.0 

163 

325. 4 

201 

393.8 

12 

53.6 

50 

122.0 

88 

190.4 

126 

258.8 

164 

327.2 

202 

395.6 

13 

55.4 

51 

123.8 

89 

192. 2 

127 

260.6 

165 

329.0 

203 

397.4 

14 

57.2 

' 52 

125.6 

90 

194.0 

128 

262. 4 

166 

330.8 

204 

399.2 

15 

59.0 

53 

127.5 

91 

195.8 

129 

264. 2 

167 

332.6 

205 

401.0 

1G 

60.8 

54 

129.2 

92 

197.6 

130 

266.0 

168 

334.4 

206 

402.8 

17 

62.6 

55 

131.0 

93 

199.4 

131 

267.8 

169 

336.2 

207 

404.6 

18 

64.4 

56 

132.8 

94 

201.2 

132 

269.6 

170 

338.0 

208 

406.4 

19 

66.2 

57 

134.6 

95 

203.0 

133 

271.4 

171 

339.8 

209 

408.2 

20 

68.0 

58 

136.4 

96 

204.8 

134 

273.2 

172 

341.6 

210 

410.0 

21 

69.8 

59 

138.2 

97 

206. 6 

135 

275.0 

173 

343.4 

220 

428.0 

22 

71.6 

60 

140.0 

98 

208.4 

136 

276.8 

174 

345.2 

230 

446.0 

23 

73.4 

61 

141.8 

99 

210.2 

137 

278.6 

175 

347.0 

240 

464.0 

24 

75.2 

62 

143.6 

100 

212.0 

138 

280.4 

176 

348.8 

250 

482.0 

25 

77.0 

63 

145.4 

101 

213.8 

139 

282.2 

177 

350.6 

260 

500.0 

26 

78.8 

64 

147.2 

102 

215.6 

140 

284.0 

178 

352.4 

270 

518.0 

27 

80.6 

65 

149.0 

103 

217.4 

141 

285.8 

179 

354.2 

280 

536.0 

28 

82.4 

66 

150.8 

104 

219.2 

142 

287.6 

180 

356.0 

290 

554.0 

29 

84.2 

67 

152.6 

105 

221.0 

143 

289.4 

181 

357.8 

300 

572.0 

30 

86.0 

68 

154.4 

106 

222.8 

144 

291.2 

182 

359.6 

350 

662.0 

31 

87.8 

69 

156.2 

107 

224.6 

145 

293.0 

183 

361.4 

400 

752.0 

32 

89.6 

70 

158.0 

108 

226.4 

146 

294.8 

184 

363.2 

450 

842.0 

33 

91.4 

71 

159.8 

109 

228.2 

147 

296.6 

185 

365.0 

500 

932.0 

34 

93.2 

72 

161.6 

110 

230.0 

148 

298.4 

186 

366.8 

550 

1,022.0 

35 

95.0 

73 

163.4 

111 

231.8 

149 

300.2 

187 

368.6 

600 

1,112.0 

36 

96.8 

74 

165.2 

112 

233. 6 

150 

302.0 

188 

370.4 

650 

1,202.0 

37 

98.6 

75 

167.0 

113 

235.4 

151 

303.8 

189 

372.2 

700 

1,292.0 


FORMS FOR REPORTING TESTS. 


FILE CARDS. 


United States Department of Agriculture, 

OFFICE OF PUBLIC ROADS, 


Washington , I). C. 


Sample No. 


Known as. 


Distillation— 


%by 

vol 


% by 

wt. 


Report on 
Identification mark 
Submitted by 
Examined for 

General character 

Specific gravity 25°/25°C . 

Melting point °C. 

Float test at.°C- 

Bitumen soluble in CS 2 . -. 
Free carbon (insol. in CS 2 ) 
Ash. 


Water. 

First light oils to 110° C. 

Second light oils 110°-170° C. 

Heavy oils 170°-270° C. 

Heavy oils 270°-315°C. 

Pitch residue. 

Total. 


.B. 


Remarks. 

Date received 


, Date reported 


Analyst 










































































44 


EXAMINATION OF BITUMINOUS ROAD MATERIALS. 


United States Department of Agriculture, 

OFFICE OF PUBLIC ROADS, 

Washington , D. C. 


Report on 
Identification mark.. 

Submitted by. 

Examined for. 

General character. 


Sample No 


Known as 


Character of residue 


Specific gravity 25°/25° C. 

Flash point °C. 

Burning point °C. 

Melting point °C. 

Viscosity at.. .°C.. .c. c. specific... 

Float test at_°C... 

Penetration test at_ °C. 

Loss at_°C_hours. 

Remarks. 

Date received., Date reported.. 


Consistency of residue 


(Float test at_°C.. 

{Penetration at... °C.. 


Bitumen soluble in CS 2 . 

Organic matter insoluble. 

Inorganic matter insoluble. 

°/c total bitumen insol. in 86° B. naphtha_ 

% total bitumen insol. in CC1 4 . 

Fixed carbon. 


Analyst.B.P 


United States Department of Agriculture, 

OFFICE OF PUBLIC ROADS, 

Washington, D. C. 


Report on 
Identification mark.. 

Submitted by. 

Examined for. 


Sample No 


Known as 


Remarks. 

Date received., Date reported. Analyst.B 

REPORT BLANKS. 

United States Department of Agriculture, 

OFFICE OF PUBLIC ROADS, 

Washington , I). C. 


Sample No. 

Report on 
Identification mark. 

Known as. 

Submitted by. 

Examined for. 


Date 


P 


Remarks 









































































APPENDIX. 


45 


United States Department of Agriculture, 

OFFICE OF PUBLIC ROADS, 

Washington, I). C., 

Date. 

Sample No. 

Report on. 

Identification mark. 

Known as..... 

Submitted by. 

Examined for. 

General characteristics. 

Specific gravity 25°/25® C.... 

Melting point °C. 

(Float test.°C., time. 

on8 stency|p enetration 25 o 100 g m s., 5 seconds. 

Viscosity at. °0.c. c. specific. 

Flash point °C. 

Burning point °C. 

Binding value. 

Loss at 163° C., 5 hours. 

Character of residue... 

Consistency of residue|p enetration . 2 5° C 100 gms., 5 seconds. 

Binding value of residue. 

Bitumen soluble in CS 2 (total bitumen). 

Organic matter insoluble. 

Inorganic matter insoluble. 

Per cent of total bitumen insoluble in 86 ° B. naphtha. 

Per cent of total bitumen insoluble in CC1 4 . 

Fixed carbon. 

Distillation— 

Char- Per cent Per cent 
acter. by vol. by wt. 

Water. 

First light oils to 110° C. 

Second light oils 110°-170° C. 

Heavy oils 170°-270° C. 

Heavy oils 270°-315°C. 

Pitch. 

Remarks. 


o 













































































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